This is needed to run Python on the Hurd, especially during the build of
python-boot0.

Adapted from https://salsa.debian.org/glibc-team/glibc/-/blob/glibc-2.31/debian/patches/hurd-i386/unsubmitted-clock_t_centiseconds.diff

Use the realtime clock for the monotonic clock. This is of course not a proper
implementation (which is being done in Mach), but will permit to fix at least
the iceweasel stack.

vlc however doesn't build when _POSIX_CLOCK_SELECTION is enabled but
_POSIX_TIMERS is not, and they refuse to fix that (see #765578), so disable the
former.

From 0aa1dfd580cf9ad7b812c307b128decb782b825f Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Mon, 2 Mar 2020 18:59:04 +0100
Subject: [PATCH 2/2] Use realtime clock for the monotonic clock.

---
 sysdeps/mach/clock_gettime.c       | 2 +-
 sysdeps/mach/hurd/bits/posix_opt.h | 6 +++---
 sysdeps/posix/clock_getres.c       | 1 +
 sysdeps/pthread/timer_create.c     | 2 +-
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/sysdeps/mach/clock_gettime.c b/sysdeps/mach/clock_gettime.c
index ac3547df3c..af8681ba4e 100644
--- a/sysdeps/mach/clock_gettime.c
+++ b/sysdeps/mach/clock_gettime.c
@@ -25,7 +25,7 @@
 int
 __clock_gettime (clockid_t clock_id, struct timespec *ts)
 {
-  if (clock_id != CLOCK_REALTIME)
+  if (clock_id != CLOCK_MONOTONIC && clock_id != CLOCK_REALTIME)
     {
       errno = EINVAL;
       return -1;
diff --git a/sysdeps/mach/hurd/bits/posix_opt.h b/sysdeps/mach/hurd/bits/posix_opt.h
index 0050151332..27b3a28ab7 100644
--- a/sysdeps/mach/hurd/bits/posix_opt.h
+++ b/sysdeps/mach/hurd/bits/posix_opt.h
@@ -163,10 +163,10 @@
 #define _POSIX_THREAD_PROCESS_SHARED	-1
 
 /* The monotonic clock might be available.  */
-#define _POSIX_MONOTONIC_CLOCK	0
+#define _POSIX_MONOTONIC_CLOCK	200809L
 
-/* The clock selection interfaces are available.  */
-#define _POSIX_CLOCK_SELECTION	200809L
+/* The clock selection interfaces are not really available yet.  */
+#define _POSIX_CLOCK_SELECTION	-1
 
 /* Advisory information interfaces could be available in future.  */
 #define _POSIX_ADVISORY_INFO	0
diff --git a/sysdeps/posix/clock_getres.c b/sysdeps/posix/clock_getres.c
index fcd79fd554..1dd02aa449 100644
--- a/sysdeps/posix/clock_getres.c
+++ b/sysdeps/posix/clock_getres.c
@@ -52,6 +52,7 @@ __clock_getres (clockid_t clock_id, struct timespec *res)
   switch (clock_id)
     {
     case CLOCK_REALTIME:
+    case CLOCK_MONOTONIC:
       retval = realtime_getres (res);
       break;
 
diff --git a/sysdeps/pthread/timer_create.c b/sysdeps/pthread/timer_create.c
index 9d8a9ea8ae..3430582c09 100644
--- a/sysdeps/pthread/timer_create.c
+++ b/sysdeps/pthread/timer_create.c
@@ -48,7 +48,7 @@ timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
       return -1;
     }
 
-  if (clock_id != CLOCK_REALTIME)
+  if (clock_id != CLOCK_REALTIME && clock_id != CLOCK_MONOTONIC)
     {
       __set_errno (EINVAL);
       return -1;
-- 
2.24.0

